StringBuffer performance

In the below code, I wanted to check the time taken by StringBuffer to do a concatination, by passing the string in two different ways. I got 750ms and 450ms respectively. What is wrong in passing the string in my second approach?Would be nice if anyone explains me theory behind this. Thanks a lot.

StringTest1 s = new StringTest1(); long rep = 1000000; long startTime = System.currentTimeMillis(); for (long l = 0; l < rep; l++) { String t1 = s.getS1(); String t2 = s.getS2(); StringBuffer s3 = new StringBuffer(t1 + File.pathSeparator + t2); } long totalTime = System.currentTimeMillis() - startTime; System.out.println("Total time = " + totalTime); System.out.println(); startTime = System.currentTimeMillis(); for (long l = 0; l < rep; l++) { StringBuffer sA = new StringBuffer(s.getS1()); sA.append(File.pathSeparator); sA.append(s.getS2()); } totalTime = System.currentTimeMillis() - startTime; System.out.println("Total time = " + totalTime); System.out.println(); }

Nothing.

What result did you expect? You do the costly string concatenation in line 16 before handing over the concatenated string to the StringBuffer. So no surprise it is slower.